HONG KONG — As Asian cities push for a stronger presence in the cruise industry, alarm is being raised in Hong Kong about the huge impact these ships have on the city’s air pollution.

Hong Kong is building a new cruise terminal for these opulent and sleek ships to dock, but some activists are urging the government to take measures to lessen the harmful effects that these ships have on the city’s air by installing electricity outlets for cruiseliners to plug into when berthed — and requiring them to do so.

It is a solution that cruise operators have said is an unrealistic demand, since older ships do not have such capabilities.

Emissions from berthed ships are considered the No. 1 contributor to Hong Kong’s severe air pollution problem and are said to account for 40% of greenhouse gases within its borders. Coming from cruise and cargo ships, these emissions outdo that of power plants and road vehicles.

“For the last 10 years, the government has done nothing to improve this,” said Melonie Chau, senior environmental affairs officer at Friends of the Earth in Hong Kong. “The government should do more to encourage or give more incentive or administrative measures to push the industry to help Hong Kong be a green port,” Chau said.

And it seems that now, small steps are being taken to address the situation.

Last week, Hong Kong’s leader, Leung Chun-ying, announced in a policy address that the government will look into requiring ships to switch to low-sulfur diesel when they are berthed in the Pearl River Delta, which encompasses areas surrounding the city.

Discussions are still in early stages, and it will take several years for this plan to be put into place, according to Chau.

The government has also said that the new cruise ship terminal, which is currently under construction and slated to open this year, will provide on-shore power supplies, allowing ships to be plugged into electric power on land and reducing emissions.

At a cruise forum last week, Pier Luigi Foschi, the chief executive of Carnival Asia, a major cruise operator, said it is unrealistic to require ships to use on-shore power because many existing ships are not equipped to be plugged in. He said that switching to cleaner fuel would be an easier option for the industry.

The discussions come at a time when the cruise industry is expanding in Asia. The Chinese airline and property company HNA has just set sail its first cruise ship from Sanya, a resort town in China, to Vietnam. Taiwan is also investing $360 million in upgrades for its two cruise terminals.

Foschi said at the forum that he expects seven million cruise passengers to come from Asia by 2020.

Container ships have in recent years also been asked, but not required, to switch to low-sulphur fuel when entering Hong Kong waters.

But those complying with the request are getting fed up with the extra cost of doing so. Earlier this month, Bloomberg reported that Maersk, the shipping giant, said that it would stop switching to clean fuel, which it had been doing voluntarily, unless the city required its rivals to do so too.

Hong Kong’s smog is considered a major health threat. A study by the University of Hong Kong linked air pollution to 1,200 deaths per year. A local think tank, Civic Exchange, has put the number of air-pollution-related deaths at 3,000 per year. The city is also one of the busiest ports in the world.